Cr3C2, VC, TaC, NbC, ZrC and their certain combinations are commonly added to WC-Co-based cemented carbides as grain-growth inhibitors. The solubility of these grain-growth inhibitors in the binder phase is an important knowledge in the development of cemented carbides. Thermodynamic calculations have been carried out to design the alloy compositions of WC-Co-based model alloys with high Co contents. The calculations are compared to the data obtained on model alloys, which were characterised by means of X-ray diffraction (XRD), light-optical microscopy (LOM) and wavelength-dispersive electron-probe microanalysis (WDS-EPMA). Extensive thermodynamic calculations were performed and compared with the experimental data from our work and those reported in the literature. A good agreement between calculation and experiment thereby validates the accuracy of our established thermodynamic database of the cemented carbides.